Stages in cell division of the rickettsia, Coxiella burneti, in host cells is being studied with the electron microscope. Also, interactions between C. burneti and its host cells is under investigation, with emphasis on cytopathic effects and the host cell's lysosomal response as determined by cytochemical tests for acid phosphatase activity. Host cell systems include both mouse L cells and Vero cells. Microtubular elements are being studied in axons and glial cells of crayfish nerve cord, using both electron microscopic and biochemical methods. Tubulin from nerve cord is being isolated and polymerized in vitro under various conditions of assembly. Autoradiographic and ligation studies are being used to test the hypothesis that microtubules may be indirectly involved in axoplasmic transport by providing guideways and attachment sites along which transport occurs. Also, studies are underway of the in vitro assembly of purified bovine brain tubulin, with emphasis on structural interactions of tubulin. BIBLIOGRAPHIC REFERENCES: Pierson, G. B., P. R. Burton, and R. H. Himes, 1976. Tubulin isolation and polymerization in the presence and absence of glycerol. J. Cell Biol., 70: 312a (abstract). Lewis, J. C. and P. R. Burton, 1977. Distribution and cytochemistry of microtubules and neurofilaments in the superior cervical trunk of the mouth. J. Comp. Neurol., in press.